Method for fabricating dual damascene structures using photo-imprint lithography, methods for fabricating imprint lithography molds for dual damascene structures, materials for imprintable dielectrics and equipment for photo-imprint lithography used in dual damascene patterning

ABSTRACT

The process of producing a dual damascene structure used for the interconnect architecture of semiconductor chips. More specifically the use of imprint lithography to fabricate dual damascene structures in a dielectric and the fabrication of dual damascene structured molds.

This is a divisional application of U.S. patent application Ser. No.10/799,282, filed Mar. 13, 2004, the priority of which is herebyclaimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to the process of producing a dualdamascene structure used for the interconnect architecture ofsemiconductor chips. More specifically this invention addresses thenovel use of imprint lithography for fabricating dual damascenestructures in a dielectric and the novel fabrication of dual damascenestructured molds for improved manufacturing throughput, processsimplification, and cost reduction, and equipment to implement dualdamascene imprint lithographic methods.

2. Description of Related Art

The conventional lithographic process involves the projection of apattern from a mask onto a substrate wherein the mask comprises a set orseries of patterns consisting of opaque and transparent regions. Thesubstrate contains a photosensitive polymer thereon. There are two typesof photoresists: positive and negative which are explained in greaterdetail below.

The fabrication of Very-Large Scale Integrated (VLSI) or Ultra-LargeScale Integrated circuit (ULSI) requires metallic wiring that connectsindividual devices in a semiconductor chip, to one another. Theresultant product of one method of creating this wiring network on asmall scale is the dual damascene (DD) process schematically shown inFIG. 1. An alternative depiction of this type product is disclosed inDeal, M; et al.; Silicon VLSI Technology: Fundamentals, Practice, andModeling, Prentice, Upper Saddle River N.J. (2000) p. 724.

In FIG. 1 a, depicting a cross section of a product of the standard DD1process, an interlayer dielectric (ILD), shown as two layers PA1-110,PA1-120 is coated on the substrate PA1-100, FIG. 1 a. The via leveldielectric PA1-110 and the line level dielectric PA1-120 are shownseparately for clarity of the process flow description. In general,these two layers can be made of the same or different insulating films,and in the former case, can be applied as a single monolithic layer. Ahard mask layer(s) PA1-130 is optionally employed to facilitate etchselectivity and to serve as a polish stop as will be discussed later.

The wiring interconnect network consists of two types of features: linefeatures that traverse a distance across the chip in a horizontal plane,and the via features which connect lines in different levels together ina vertical plane. Historically, both layers are made from an inorganicglass-like silicon dioxide (SiO₂) or a fluorinated silica film depositedby plasma enhanced chemical vapor deposition (PECVD).

In the conventional dual damascene process, the position of thehorizontal lines PA1-150 and the vertical vias PA1-170 are definedlithographically in photoresist layers, PA1-140, depicted in FIGS. 1 band 1 d respectively, and transferred into the hard mask and ILD layersusing reactive ion etching processes.

The results of the process sequence shown in FIG. 1 c is called a“line-first” approach because the trench PA1-160 which will house theline feature is etched first. After the trench formation, lithography isused to define a via pattern PA1-170 in the photoresist layer PA1-140,which is transferred into the dielectric material to generate a viaopening PA1-180, FIG. 1 d. The dual damascene trench and via structurePA1-190 is shown in FIG. 1 e after the photoresist has been stripped.This structure PA1-190 is coated with a conducting liner material ormaterial stack PA1-200 that serves to protect the conductor metal linesand vias and serve as an adhesion layer between the conductor and theILD. This recess is then filled with a conducting fill material PA1-210over the surface of the patterned substrate. The fill is most commonlyaccomplished by electroplating of copper, although other methods such asCVD and other materials such as Al or Au can also be used. The fill andliner materials are then chemically-mechanically polished (CMP) to becoplanar with the surface of the hard mask and the structure at thisstage is shown in FIG. 1 f.

A capping material PA1-220 is deposited over the metal or as a blanketfilm, as is depicted in FIG. 1 g to passivate the exposed metal surfaceand to serve as a diffusion barrier between the metal and any additionalILD layers to be deposited over them. Silicon nitride, silicon carbide,and silicon carbonitride films deposited by PECVD are typically used asthe capping material PA1-220. This process sequence is repeated for eachlevel of the interconnects on the device. Since two interconnectfeatures are defined to form a conductor in-lay within an insulator by asingle polish step, this process is designated a dual damascene process.

Printed publications which provide a background for the presentinvention and which are hereby incorporated by reference and made a partof this disclosure are: U.S. Pat. No. 6,696,224, Template for RoomTemperature, Low Pressure Micro- and Nano-Print Lithography; U.S. Pat.No. 6,334,960, Step and Flash Imprint Lithography; U.S. PublicationApplication Number 20020098426; High-Resolution Overlay AlignmentMethods and Systems for Imprint Lithography; U.S. PublicationApplication Number 20020094496 Method and System of Automatic FluidDispensing for Imprint Lithography; U.S. Publication Application Number20020093122, Methods for High Precision Gap and Orientation SensingBetween a Transparent Template and Substrate for Imprint Lithography;U.S. Publication Application Number 20040022888, Alignment Systems forImprint Lithography; U.S. Publication Application Number 20040021254,Alignment Methods for Imprint Lithography; U.S. Publication ApplicationNumber 20040009673, Method and System for Imprint Lithography Using anElectric Field; U.S. Publication Application Number 20040008334, Stepand Repeat Imprint Lithography Systems; U.S. Publication ApplicationNumber 20040007799, Formation of Discontinuous Films During an ImprintLithography Process; U.S. Publication Application Number 20020115002,Template for Room Temperature, Low Pressure Micro- and Nano-imprintLithography, U.S. Publication Application Number 20020098426, HighResolution Overlay Alignment Methods and Systems for ImprintLithography, U.S. Publication Application Number 20020094496, Method andSystem of Automatic Fluid Dispensing for Imprint Lithography Processes;U.S. Publication Application Number 20020093122, Methods forHigh-Precision Gap and Orientation Sensing Between a TransparentTemplate and Substrate for Imprint Lithography.

SUMMARY OF THE INVENTION

The present invention pertains: (a) to the fabrication of dual damascenestructures using imprint lithographic techniques; (b) to the fabricationof dual damascene relief structures in imprint lithography molds; (c) tothe design of equipment for imprinting dual damascene structures; (d)and to the formulation of material for dual damascene imprintlithography.

While the description of the present invention is predominatelydiscussed herein in terms of “photolithography,” it is to be understoodthat where that term is used in the discussion of the invention, itshall include and be equally applicable to systems that use heat andpressure as well as light or any combination of these systems.

The method of the present invention includes (a) a means, such as amask, for fabricating a dual damascene structure in a reactiveion-etch-resistant material which is used to transfer its pattern into ainterlayer dielectric, (b) a means for fabricating a dual damascenestructure in a material suitable for an interlayer dielectric, (c) ameans for fabricating a dual damascene structure in a material which isconverted into an interlayer dielectric through a thermal anneal, (d) ameans for fabricating a dual damascene structure in a material which isconverted into an interlayer dielectric through a chemical treatment,(e) a means for fabricating a dual damascene structure in a materialwhich is converted into an interlayer dielectric through a combinationof a thermal anneal process and chemical treatment process, (f)imprintable material formulations that render an etch-resistant materialwhen imprinted, (g) formulations that render an interlayer dielectricmaterial, (h) formulations that render a dual damascene structure, butrequire subsequent thermal, plasma, and/or chemical treatment togenerate an interlayer dielectric material, (i) chemical treatment of animprinted material that includes wet-chemical, vapor, or plasmatreatment, (j) additives to imprintable solutions that increase theadhesive strength of the imprint material—substrate interface such asmultifunctional coupling agents, (k) additives to imprintable solutionsthat decrease the adhesive strength of the imprint material—moldinterface, (l) a means of fabricating a multilevel mold that contains adual damascene relief structure, (m) imprinting dual damascenestructures with imprint equipment that contain flexures for X,Y, or Zpositioning, and/or α, β, or γ tilting, (n) imprinting dual damascenestructures with imprint equipment that contain Z-gap control, (o)imprinting dual damascene structures with imprint equipment that allowsfor layer-to-layer overlay, (p) imprint dual damascene structures withequipment that uses pattern recognition for overlay, (q) incorporatingoverlay and/or alignment structures into a dual damascene mold, (r)imprinting materials in a dual damascene structure that remain in thesubstrate, (s) performing a reactive ion etch that removes residualimprinted material allowing for electrical contact between the linelevel metal in a dual damascene structures and the underlying conductivepattern, (t) coating a dual damascene mold structure with a low surfaceenergy film including fluorinated self-assembly monolayers, (u)utilizing gap sensing equipment to recognize position of the dualdamascene mold's closest surface, (v) utilizing a microdroplet patternto optimize uniformity of dual damascene imprint, (w) utilizing a spincoated imprint resin solution that allows a dual damascene imprint.

More specifically, one method for producing a multilevel mold thatcontains the relief image of a dual-damascene structure or the negativerelief image of a dual-damascene structure in accordance with thepresent invention comprises the steps of: coating a substrate with aresist material, said resist material having a top surface; patterningthe resist material with a negative line level pattern; etching saidnegative line level pattern into said substrate to form a negative vialevel topography transferred in an upper surface of said substrate;coating said upper surface of said substrate with a planarizing layer;coating said planarizing layer with a resist and patterning said resistcoating with a negative line level pattern; removing said layersresulting in a shaped article having a negative dual damascene relieftopography.

Another method for producing a multilevel mold that contains the reliefimage of a dual-damascene structure or the negative relief image of adual-damascene structure comprises the steps of: coating a substratewith a hardmask stack having a plurality of layers, the aforementionedplurality of layers includes a bottom etchstop layer which is in contactwith a surface of said substrate; a middle layer suitable for printing anegative line-level pattern, said middle layer being in contact with anexposed surface of said bottom layer; and a top layer suitable forprinting a negative line level pattern, said top layer being in contactwith an exposed surface of said middle layer; then coating an exposedsurface of said top layer of said hardmask stack with a resist; saidresist material having a top surface; generating a negative via-levelpattern in said top surface of said resist material; transferring saidnegative via-level pattern into said top layer of said hardmask stackand into said substrate thereby forming a negative line-level patterntransferring said negative line-level pattern and said negative vialevel pattern through said middle and bottom layers to form a relief ofa dual damascene structure; removing the hardmask layers resulting in anegative dual damascene relief structure and patterning said resistmaterial with a negative line level pattern; etching said negative linelevel pattern into said substrate to form a negative via leveltopography transferred in an upper surface of said substrate; coatingsaid upper surface of said substrate with a planarizing layer; coatingsaid planarizing layer with a resist and patterning said resist coatingwith a negative line level pattern; removing said layers resulting in ashaped article having a negative dual damascene relief topography.

In order to form the structure of the present invention, a combinationof elements is used which together, acting in cooperation, provide thenovel article described herein. The system includes the followingelements:

-   -   a. A substrate handling system    -   b. A substrate stage    -   c. A mold stage    -   d. An irradiation system    -   e. A mold-substrate orientation control system    -   f. A mold fixture    -   g. A substrate fixture    -   h. A curable material dispensing system    -   i. A nitrogen purge system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood by reference to thefollowing detailed description of the preferred embodiments of thepresent invention when read in conjunction with the accompanyingdrawings, in which like reference characters refer to like partsthroughout the views and in which:

FIG. 1 depicts a Dual Damascene Process as found in the Prior Art.

FIG. 2 depicts cross sectional views of Articles formed from the DualDamascene Fabrication Process of the present invention usingPhotoimprint Lithography to Define a Pattern in a Photo-sensitive Layerthat meets the requirements of an Interlayer Dielectric.

FIG. 3 depicts alternate cross sectional views of Articles formed fromthe Dual Damascene Fabrication Process of the present invention usingPhotoimprint Lithography to Define a Pattern in a Photo-curable materialand subsequently transferred into an Interlayer Dielectric Layer.

FIG. 4 depicts cross sectional views of articles resulting from the MoldFabrication Process for Dual Damascene Relief Structure of the presentinvention.

FIG. 5 depicts cross sectional views of articles resulting from the MoldFabrication Process for Dual Damascene Relief Structure using aMultilayer Hardmask Stack.

FIG. 6 is a micrograph of a Relief structure of a dual damascene imprintmold.

FIG. 7 is a chart disclosing the Dielectric Constant of twophotocrosslinkable dielectric films.

FIG. 8 is a graph depicting Dielectric Breakdown and Leakage as afunction of Electric Field.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, reference is made to the accompanyingdrawings which form a part hereof and which illustrate severalembodiments of the present invention. It is understood that otherembodiments may be utilized and structural and operational changes maybe made without departing from the scope of the present invention.

As discussed above, current methods of manufacturing a dual damascenestructure require a multitude of lithography, reactive ion etch, anddeposition steps as shown in FIG. 1 in order to generate a DualDamascene structure. Typically two lithography steps are required. Foreach lithography step, there may be several reactive ion etch stepsrequired to open the antireflective coating, hardmask stack(s), and thedielectric material itself. The present invention is an improvement ofthe procedures found in the prior art.

In the first embodiment, shown in FIG. 2 a, an imprint lithography mold,2-240, is brought into proximity of a “substrate stack” comprising acoating of a photo-curable dielectric material 2-230 atop a substrate,2-100, said stack being aligned to an underlying pattern (not shown).Mold 2-240 is brought into contact with the substrate stack (comprising2-100 and 2-230), and the combination is exposed to actinic light,pressure, and/or heat, 2-250, FIG. 2 b to cure the photo-curableinterlayer dielectric material, 2-230.

Once the photo-curable interlayer dielectric material is cured, the moldis removed leaving behind the relief structure, 2-260, of the mold (Seethe configuration of 2-240 of FIG. 2 a) which has been designed to bethe appropriate dual damascene structure. A small amount of curedresidual material, 2-270, remains, FIG. 2 c. Cured residual material2-270 must be removed for line-via-line metallic contact to be made.This is removed during a short reactive ion etch to leave the final dualdamascene structure as shown in FIG. 2 d.

The final dual damascene structure, 2-190, in the photo-cured interlayerdielectric as shown in FIG. 2 d is then coated with liner, 2-200, andmetalized, 2-210. As shown in FIG. 2 e, liner 2-200 and metal 2-210 arepolished to the surface of interlayer dielectric 2-260. Then a caplayer, 2-220, is put down selectively or, as shown in FIG. 2 e, is putdown in a blanket film. This structure is then ready for another levelbuild which repeats the steps detailed above.

In second preferred embodiment, shown in FIG. 3, an imprint lithographymold, 3-240, is brought into proximity of a “substrate stack” comprisinga coating of an interlayer dielectric material 3-280 and a photo-curablematerial, 3-290 atop a substrate, 3-100, said stack being aligned to anunderlying pattern (not shown). The mold is brought into contact withthe substrate stack comprising 3-100, 3-280, 3-290, which is exposed toactinic light, pressure, and/or heat, 3-250, as depicted in FIG. 3 b.

Once the photocurable material is cured, the mold is removed, as shownin FIG. 3 c, leaving behind the relief structure, 3-260, of the mold(See the configuration of 3-240 of FIG. 3 a) which has been designed tobe the appropriate dual damascene structure. A small amount of curedresidual material, 3-270, remains. The dual structure in the photocuredimprint resin is then used as a reactive ion etch mask during theinterlayer dielectric etch to produce the dual damascene structure,3-190, shown in FIG. 3 d. The imprint resin is used to generate amultilayer resist-based hardmask to transfer each of the two layers(line and via) into the interlayer dielectric.

The final dual damascene structure in the interlayer dielectric is thencoated with a liner, 3-200, and metalized 3-210. The liner and metal arepolished to the surface of the interlayer dielectric. Then a cap layer,3-220, is put down selectively over the metal lines or, as shown FIG. 3e, is put down in a blanket film. This structure is then ready foranother level build which repeats the steps detailed above.

In order to reduce the process complexity and facilitate multilevelimprint lithographic patterning, the mold or template must be fabricatedwith the appropriate multilayered structure. As shown in FIGS. 2 and 3,the mold would then be used to replicate its relief structure on thesurface of a substrate in a moldable material. As shown above, thereplica could be used in either of the two embodiments.

In the first embodiment, the material in which the relief is generatedwould be used as the interlayer dielectric. In the second embodiment,the relief structure in the imprinted material would be used to reactiveion etch the relief into an underlying material.

The method of mold fabrication follows advanced phase shift reticlemanufacturing techniques and traditional dual damascene maskingmethodologies. Examples of such methodologies are found in Proceedingsof Advanced Metallization Conference, Tim Dalton, et al., pps 85-89, MRS(2004), the contents of which are hereby incorporated by referenceherein. Two reactive ion etches and two lithography steps would berequired to print a multilayered pattern on the surface of the moldsubstrate using traditional imaging techniques such as electron beam,ion beam (projected or focused), optical pattern generators (photons),scanning probes, or similar techniques. Alternative imaging solutionssuch as advanced interferometric lithography could also be used to imagethe multilayered structure onto the surface. Two approaches for the moldfabrication process are depicted in FIG. 4 and FIG. 5. In FIG. 4, amultilayer lithographic scheme is depicted.

As noted above, there are two types of photoresists: positive andnegative. For positive resists, the resist is exposed to, for example,UV light, wherever the underlying material is to be removed. In theseresists, exposure to a source of radiation, or some other activatingmeans such as UV light, changes the chemistry of the resist so that itbecomes more soluble in a developer. The exposed resist is then washedaway by the developer solution. The mask in this case contains an exactreplica of the pattern which remains on the substrate.

In a negative resist, the exposure to the activating means, such as UVlight causes the negative resist to become polymerized, strengthened andessentially insoluble in the developer solution. Thus, the negativeresist remains on the surface wherever it is exposed. The system isanalogous to a photographic negative which contain substantiallytransparent and substantially opaque areas. In this negative system, theareas under the transparent areas are polymerized and the areas underthe opaque areas are not and wash away with the application of thedeveloper solution. The negative image of the image of the mask istransferred to the resist. The present invention utilizes the “negative”resist.

The negative line level and negative via level pattern in the moldgenerate a negative of the dual damascene structure. Thus the imprintedrelief equates to the dual damascene structure.

In FIG. 4 a, a mold substrate, 4-100, is coated with a resist material,4-110. This resist material is patterned with a negative via-levelpattern resulting in the topography 4-120 as depicted in FIG. 4( b).This pattern is then etched into the substrate leaving a negativevia-level topography transferred into the substrate as shown in FIG. 4b. A planarizing layer, 4-130, is used to coat over the substrate. Aresist, 4-140, is then coated over this layer and patterned with anegative line-level pattern, 4-150, as shown in FIG. 4 c. This negativeline pattern is then used to etch into the substrate to generate anegative line pattern, 4-160, in the mold substrate as in FIG. 4 d. Thelayers are then removed to leave the desired negative dual damascenerelief topography, 4-190R. This topography is then used as a mold,4-240, shown in FIG. 4 f. As indicated in FIG. 4 f, this can then beused as a mold, 4-240, in the imprint patterning steps for thepatterning steps in forming the articles depicted in FIG. 2 (2-240) andFIG. 3 (3-240). It should be noted that the order of the patterning canbe either via-first or line-first.

A second embodiment of the mold fabrication process of the presentinvention utilizes a trilayered hardmask scheme. The particular numberof hardmask in this scheme is representative and does not limit theapproach to three layers.

In FIG. 5 a, a mold substrate, 5-100, is coated with a trilayer hardmaskstack comprising three distinct layers, 5-110, 5-120, and 5-130. Thebottom hardmask 5-110 serves as an etch-stop layer as depicted in FIG.5. The middle hardmask 5-120 is used to print the negative line-levelpattern. The top layer 5-130 is used to pattern the negative via levelpattern. Upon this stack, a resist, 5-140 is coated (FIG. 5 a). As shownin FIG. 5 b, a negative via-level pattern is generated in the resist.This negative via-level pattern is transferred into the top hardmasklayer, 5-130, to generate a topographical pattern, 5-150. A resist,5-170, is coated over topography of the 5-130 hardmask and patternedwith a negative line-level pattern and then reactive ion etched throughthe hardmask stack (i.e., 5-110, 5-120, 5-130) and into the substrate,5-100, to leave the negative line-level pattern, 5-160, as shown in FIG.5 c. In FIG. 5 d, the transfer of the negative line-level pattern,5-160, and the negative via-level is transferred through the twohardmasks (5-120, 5-130) to generate the relief of a dual damascene-likestructure, 5-180R, that retains the patterned hardmask 5-115 which isused to protect the top surface of the mold (FIG. 5 d.). The hardmask5-115 is removed to leave the appropriate negative dual damascene reliefstructure, 5-190R (FIG. 5 e). As indicated in FIG. 5 f, this can then beused as a mold, 5-240, in the imprint patterning steps for thepatterning steps of FIGS. 2 and 3 (2-240, 3-240). In FIG. 5 f, element5-01 depicts the back of the structure to be formed, the negative lineis 5-02 and the negative via is depicted at 5-03.

While the invention is described in terms of a via exposure methodologyfirst, as depicted in FIGS. 4 and 5, a line first exposure methodologyis equally practicable by those skilled in the art.

The mold described above is fabricated from a variety of inorganic andorganic materials. Several examples of are silicon, silicon dioxide,silicon nitride, diamond-like carbon, silsesquioxane, alumina, indiumtin oxide, gallium arsenide. Further, polymers such aspoly(methylmethacrylate), polystryrene, polycarbonate,polytetrafluoroethane, or any other appropriate material by itself, acomposite material or a layered material that meets the mechanical,optical and thermal requirements. Each level (line level and via level)of the mold may be composed of different materials listed above allowingease of fabrication.

The modulus should be greater than 10 MPa and have a strength greaterthan 10 MPa. The thickness and size of the mold are dictated by theapplication. A wafer scale mold would necessarily be larger in diameter.For photocuring, either the substrate or the mold must be transparent tothe wavelength to which the photocurable material is sensitive.

The advantage of the imprint lithography process of the presentinvention is the minimization of the process steps required to fabricatethe multilayered dual damascene structure and elimination of hardmaskmaterials and associated equipment. In conventional processing, alithography step is used to define one layer at a time. In this process,a single process creates a multilayered structure. The hardmaskdeposition process, the two conventional lithography steps, and the tworeactive ion etchs of the prior art are replaced with a single imprintlithography step followed by one short etch that allows good electricalcontact to the underlying conductive pattern once metallization iscomplete. The process of the present invention eliminates alignmentdeviation that varies from lot to lot and chip to chip. The number ofalignment steps and their metrology are decreased by 50%.

The imprint lithography process of the present invention achievessubstantially improved results over the prior art by creating thenonconventional multilayer mold such that two layers are patterned in asingle step. It is especially beneficial as it is applied to dualdamascene structures where via placement is critical.

In the first embodiment, shown in FIG. 2, the imprinted material is asuitable dielectric. Therefore, only a short and less damaging etch isrequired to remove any residual material in the via. In the secondembodiment, shown in FIG. 3, the pattern is transferred using reactiveion etching into the underlying interlayer dielectric material.

An example of the relief structure that can be generated by imprintlithography is shown in FIG. 5. This example is a relief image of a dualdamascene imprint mold itself. Hence, this relief could be used as themold for a dual damascene imprint.

The imprintable material may be conveniently applied to the surface ofthe resist using a “spin coating” process that produces a uniform layerof imprintable material on the surface to which is it applied.

For the first preferred embodiment, the imprintable material must bephotosensitive and ideally have a low viscosity. This feature isdiscussed in greater detail in Colburn, M., Step And Flash ImprintLithography, A Low-Pressure, Room-Temperature Nanoimprint Lithography,Ph.D. Thesis, The University of Texas at Austin 2001, referred tohereinafter as “Colburn” and the contents of which are herebyincorporated by reference herein.

However, the photosensitive imprintable material must also act as aninterlayer dielectric. Consequently, it must exhibit sufficient thermalstability, dielectric breakdown, low dielectric loss, long-termstability of dielectric properties under stress. These properties maynot exist in the material as imprinted, but may be imparted in thematerial by a post-imprint thermal treatment, a post-imprint plasmatreatment, a post-imprint chemical treatment, or combination of thesetreatments.

The multilevel structure of the present invention is a curable materialformulated using an organic polymeric resin such aspolymethylmethacrylate, polyacrylates, polyepoxides, functionalizeddimethylsiloxanes, alkylsilanes, functionalized methsilsesquioxanes,hydrosilsesquioxanes, polyurethanes, polycyanoacrylates, polystyrenepolyvinyls, polyvinylethers, ketene acetals, cyclohexyl epoxides, apolymeric network crosslinked by a diene-dieneophile reaction comprisinga Diels-Alder reaction and polyimide. The curable material may also beformulated using an organosilicate resin such as polyhedralsilsesquioxanes, silsesquioxanes, dimethylsiloxanes, polycarbosilanes.

Further, the multilevel structure the curable material is formulatedusing conductive polymers selected from the groups consisting ofpoly(thiophene) and polyanaline.

The curable material contains any combination of initiator, resin(s),monomer(s), coupling/adhesion agent(s), release agent(s), andcrosslinking agent. In each case the curable material contains amultifunctional monomer or oligomer that serves as a crosslinking agent.It is important to note that the amount of each constituent contained inthe various compositions embodied within the scope of the presentinvention may vary because the relative proportions of each constituentwill be a function of the desired properties of the final productproduced and will be within the scope of the skilled artisan.

The low molecular weight materials noted are: methyl acrylate, methylmethacrylate, epoxides, vinyls, silyl vinyl ethers, ketenes, orfunctionalized versions of polyhedral silsesquioxanes, silsesquioxanes,dimethylsiloxanes, polycarbosilanes, and combinations thereof.

The coupling agents used are designed to form covalent bonds between thesubstrate and the cured material. Suitable coupling agents are: acrylatefunctionalized silanes, 3-acryloxypropyltrimethoxysilane, alkoxysilanesfunctionalized methacrylates, polyacrylates, polyepoxides,functionalized dimethylsiloxanes, alkylsilanes, functionalizedmethsilsesquioxanes, hydrosilsesquioxanes, polyurethanes,polycyanoacrylates, polystyrene polyvinyls, polyvinylethers, keteneacetals, a polymeric network crosslinked by a diene-dieneophile reactioncomprising a Diels-Alder reaction and polyimide.

The curable imprint material of the present invention contains releaseagents designed to minimize adhesion to a multilevel mold or template.Typical release agents are: tridecafluoro acrylate, functionalizedmethacrylates, acrylates, epoxides, cyclohexylepoxides, functionalizeddimethylsiloxanes, alkylsilanes, functionalized methsilsesquioxanes,hydrosilsesquioxanes, polyurethanes, polycyanoacrylates, polystyrenepolyvinyls, polyvinylethers, ketene acetals, a polymeric networkcrosslinked by a diene-dieneophile reaction comprising a Diels-Alderreaction.

Suitable cross-linking agent are: bis functional methacrylates,acrylates, epoxides, functionalized dimethylsiloxanes, alkylsilanes,functionalized methsilsesquioxanes, hydrosilsesquioxanes, polyurethanes,polycyanoacrylates, polystyrene polyvinyls, polyvinylethers, keteneacetals, a polymeric network crosslinked by a diene-dieneophile reactioncomprising a Diels-Alder reaction.

The multilevel structure of the present invention may containselectively decomposable and removable components in order to generate aporous structure said components forming a material being a thermallylabil material that thermally degrades above 200° C. selectively toresin. The used may be: polymethylmethacrylate, polystyrene andpolypropylene glycol.

The initiators consist of typical free radical generators such asbenzophenone free radical generator, iodonium salts, a photoacidgenerator, AIBN thermal free radical generator, a thermal acidgenerator, and any combination of the above mentioned compounds toinitiate the curing process.

The acid generator used in accordance with the present invention ispreferably an acid generator compound that liberates acid upon phototreatment. A variety of known thermal acid generators are suitablyemployed such as e.g. 2,4,4,6-tetrabromocyclohexadienone, benzointosylate, 2-nitrobenzyl tosylate and other alkyl esters of organicsulfonic acids. Compounds that generate a sulfonic acid upon activationare generally suitable. Other suitable thermally activated acidgenerators are described in U.S. Pat. Nos. 5,886,102 and 5,939,236. Thedisclosures of these two patents are incorporated herein by reference.If desired, a radiation-sensitive acid generator may be employed as analternative to a thermally activated acid generator or in combinationwith a thermally activated acid generator. Examples of suitableradiation-sensitive acid generators are also described in U.S. Pat. Nos.5,886,102 and 5,939,236. Other radiation-sensitive acid generators knownin the resist art may also be used as long as they are compatible withthe other components of the antireflective composition. Where aradiation-sensitive acid generator is used, the cure (crosslinking)temperature of the composition may be reduced by application ofappropriate radiation to induce acid generation which in turn catalyzesthe crosslinking reaction. Even if a radiation-sensitive acid generatoris used, it is preferred to thermally treat the composition toaccelerate the crosslinking process (e.g., for wafers in a productionline.)

Examples of photosensitive imprintable materials that meet therequirements set forth above include, but are not limited to,functionalized dimethylsiloxanes, alkylsilanes, functionalizedmethsilsesquioxanes, hydrosilsesquioxanes, urethanes, polyimides,parylene, polytetrafluoroethane, etc. The reactive functionalities ofthe photosensitive imprintable material, include, but are not limited tovinyl ethers, ketene acetals, diene-dieneophiles, methacrylates,acrylates, epoxides Sacrificial components of the curable dielectricmaterial may be removed to generate a porous film. These sacrificialcomponents can be tailored by composites as described in SupramolecularApproaches to Nanoscale Dielectric Foams for Advanced MicroelectronicDevices, Craig J. Hawker, James L. Hedrick, Robert D. Miller and WilliVolksen, MIRS Bulletin, April 2000, the contents of which are herebyincorporated by reference herein.

For the second embodiment, the imprintable material must bephotosensitive and ideally have a low viscosity. (See also: Coburnsupra) It must provide sufficient etch selectivity to pattern theunderlying interlayer dielectric material.

Examples of materials that meet this requirement include but are notlimited to vinyl ethers, ketene acetals, diene-dieneophiles,methacrylates, acrylates, epoxides, functionalized dimethylsiloxanes,alkylsilanes, functionalized methsilsesquioxanes, hydrosilsesquioxanes,urethanes, cyanoacrylates or other reactive monomeric or oligomericmaterials.

The mechanical and adhesive properties are also important to animprinted dielectric used in accordance with the present invention.Ideally, the material must be mechanically stable enough to withstandsubsequent processing such as chemical-mechanical polishing (CMP), orwire bonding to name a few. The material must adhere to the variousinterfaces. Preferably, the imprintable material is tailored andsuitable to accommodate interfacial bonding.

For instance, in the second embodiment, if the imprinted material ispatterned over a SiO₂ layer, and the imprinted material was an acrylate,an acrylate functionalized silane such as3-acryloxypropyl-trimethoxysilane would react with the SiO₂ as well aswith the acrylate backbone of the imprinted material. Other means, suchas utilizing a second “non photosensitive” thermally initiated reactionsuch as a condensation to improve adhesion or mechanical properties mayalso be beneficial if desired.

In order to make the imprinted material mechanically stable, somecrosslinking agent such as a multifunctional monomer may need to beadded to the imprint solution. Additionally, low surface energycomponents such as fluorinated alkyl-acrylates improve processperformance by minimizing the separation force when the mold is removedfrom the imprinted surface. The mold may also be treated with a lowsurface energy treatment such as fluorinated alkyl-silanes such as:

And the reaction for forming such composition is:

Si(OH)+Si(OH)

H₂O+—[—SiOSi—]—

The imprint mold itself must be attached to a mechanical structure thatenables the imprint to be performed. Many systems exist to perform thistask. Such systems are disclosed in Johnson, S; Selectively CompliantOrientation Stages For Imprint Lithography, MS Thesis, The University ofTexas at Austin, 1999; Chou, S. Y., P. R. Krauss, and P. J. Renstrom. J.Vac. Sci. Tech. B, 14(6) (1996) 4129; H. Tan, A. Gilbertson, and S. Y.Chou, Roller Nanoimprint Lithography,” J. VST B. 16(6), 3926-8, (1998);Colburn, M., et al.; Proc. SPIE 1999, Santa Clara, Calif., 3676(I), p.379; Nanoimprint Lithography Equipment from www.obducat.com, thecontents of which are hereby incorporated by reference herein.

However, precision flexure-based stages offer repeatable means ofperforming the motion while minimizing particle generation and shearaction. The use of a flexure stage in conjunction with a dual damascenemold offers a combination ideally suited for high resolution patterningwhile minimizing particles and maximizing reproducibility.

Ideally, the center of rotation is at the surface of the mold. However,it may be beneficial to have the center of rotation be off-set from thecentral point of mold surface but remain in the plane of the moldsurface. Using this arrangement allows for the imprint fluid to beexpelled from the gap between the mold and the substrate with lessforce. Support for this is found in Nguyen, C., AsymmetricFluid-Structure Dynamics In Nanoscale Imprint Lithography, MS Thesis,The University of Texas at Austin 2001, which is incorporated byreference herein.

Dispensing the imprintable material in droplets or a micropattern mayimprove imprint uniformity and decrease the force required to imprintthe material. For example, the system used to dispense the curablematerial can dispense same in microliter quantities, smaller droplets ora series of individual droplets. The material should be dispensed in adefined pattern such as a continuous pattern or a “W” pattern. If usinga final casting layer in the process, spin coating is also applicable.

Gap control is of particular interest when performing a dual damasceneimprint since the via pattern is less dense than the line-level pattern.Since via level pattern density is low, poor gap control can lead toenormous localized pressure generation since pressure is related toinverse of the gap distance cubed. (See: Colburn, supra.) Consequently,when the imprint is performed a z-direction gap sensing system isdesirable.

Preferably, a nondestructive system such as capacitance sensors,pneumatic sensors, piezo sensors, spectral reflectometers, single andmultiwavelength interferometers, or ellipsometers may be used for gapcontrol. Overlay of a dual damascene mold may be performed by usingembedded alignment marks that are recessed into the mold. Examples ofsuch systems are disclosed in U.S. Pat. No. 6,696,220, and in articlesby E. E. Moon, et al. JVST B 14 (6) November/December 1996 and Moon, etal. JVST B 21 (6) November/December 2003, the contents of which arehereby incorporated by reference herein.

The surface of the mold can be treated with a low surface energycomponent. The low surface energy component is a fluorinated selfassembly monolayer comprising a fluorinated alkyl halosilane,fluorinated alkyl alkoxysilane, fluorinated alkyl acetoxy silane andtridecafluorooctyltrichlorosilane.

Suitable fluorinated compounds which can be used have the generalformula:

CF₃C_(n-2)F₂C₂H₂Si(OR₁)_(3-x;3-y)(X)_(x)(R₂)_(y)

-   -   Wherein X is halogen, Cl, Br; R is alkyl C₁ to C₈; R₂ is alkyl,        methyl;    -   x=0 to 3; y=0 to 2 and n is greater than or equal to 2; and    -   x+y+(3−x−y)=3

Specific examples of the fluorinated compounds which can be used as alow surface energy component are: tridecafluorooctyl trichloro silane;tridecafluorooctyl dimethyl chloro silane; tridecafluorooctyl methyldichloro silane; tridecafluorooctyl trimethoxy silane;tridecafluorooctyl trimethoxy silane; tridecafluorooctyl diethoxy methylsilane; nonafluorohexyl trichloro silane; nonafluorohexyl dimethylchloro silane; nonafluorohexyl methyl dichloro silane; nonafluorohexyltrimethoxy silane; nonafluorohexyl trimethoxy silane; nonafluorohexyldiethoxy methyl silane.

FIG. 6 is an image of a dual damascene relief structure of an imprintmold. This particular mold was fabricated by replication of an actualdual damascene structure in accordance with the present invention. Thehighest level shown is the via level; the second level from the top isthe line level. A unique feature of the dual damascene imprint mold isthe low pattern density of the highest level which represents the moldthat will be closest to the substrate. This serves to minimize thatforce require to imprint the mold into the imprint resin.

FIG. 7 represents the dielectric constant of two photocrosslinkabledielectric materials that have been thermally cured after photo-curing.The measurement was performed in a Metal-Insulator-Semiconductorstructure where the Metal was aluminum, the insulator is the dielectricmaterial, and the semiconductor is a silicon wafer.

FIG. 8( a). shows the breakdown (leakage current greater than 1 e-5A/cm²) as a function of tested MIS structures. This isolates the defectdensity or material quality. A breakdown field of 4 MV/cm is similar toporous dielectrics currently available commercially available. FIG. 8(b) discloses the leakage current (A/cm²) for representative measurementsite versus field strength (MV/cm). Breakdown is set at Field Strengthat which leakage current greater than 1e-5 A/cm2. Leakage current isdefined as current flowing between the insulator in the MIS structureduring the test.

Thus while there have been shown and described and pointed outfundamental novel features of the invention as applied to currentlypreferred embodiments thereof, it will be understood that variousomissions, substitutions and changes in the form and details as to thecommunication system of the present invention and methods encompassedtherewith, may be made by those skilled in the art without departingfrom the spirit of the invention. In addition, it is to be understoodthat the drawings are provided for informational purposes. It is theintention therefore to be limited only as indicated by the scope of theclaims appended herewith.

1. A system comprising a plurality of elements functioning incombination to fabricate a dual damascene structure, said structurebeing formed by coating a mold substrate with a photoresist; a.Patterning said photoresist with a pattern; b. Exposing said photoresistand pattern, and developing said pattern in said photoresist; c.Transferring said pattern in said photoresist into an upper surface of amold substrate; d. Coating said upper surface of said mold substratewith a planarizing layer to form a planarized stack; e. Coating saidplanarized stack with a photoresist; f. Exposing said photoresist anddeveloping the pattern in said photoresist; g. Transferring said patterninto said mold substrate.
 2. The system defined in claim 1 whichincludes the following elements: a. A substrate handling system b. Asubstrate stage c. A mold stage d. An irradiation system e. Amold-substrate orientation control system f. A mold fixture g. Asubstrate fixture h. A curable material dispensing system i. A nitrogenpurge system.
 3. The system defined in claim 2 in which said moldfixture is designed to hold a multilevel mold and designed to imprintsaid mold into a curable material.
 4. The system defined in claim 2 inwhich actuation of said mold in a process of manufacturing a structureis performed using piezo element(s), pneumatic elements, hydraulicelements or electromagnetic actuation.
 5. The system defined in claim 2in which said mold fixture and said substrate fixture comprise flexureelements that allow for orienting said mold to the substrate in aco-planar fashion.
 6. The system defined in claim 2 in which said moldstage and/or said substrate stage comprise a stage in which a substrateis allowed to translate relative to a fixed mold.
 7. The system definedin claim 2 contains a stage in which the mold is allowed to translate aseries of lines relative to a fixed substrate.
 8. The system defined inclaim 2 wherein in said mold-substrate orientation control system adistance between a mold and a substrate is monitored by capacitance,pneumatic pressure drop, spectral reflectometry, single beam ormultiwavelength interferometry or a combination thereof.
 9. The systemdefined in claim 2 in which the distance between a mold and a referencesurface, and a substrate and a reference surface is monitored bycapacitance, pneumatic pressure drop, spectral reflectometry, singlebeam or multiwavelength interferometry or a combination thereof.
 10. Thesystem defined in claim 2 which incorporates a curable materialdispensing system.
 11. The system defined in claim 10 wherein saidcurable material deposition system dispenses microliter or smallerdroplets.
 12. The system defined in claim 10 wherein said curablematerial deposition system dispenses said curable material in a definedpattern.
 13. The system defined in claim 11 in which said curablematerial deposition system dispenses said curable material in acontinuous pattern such as a series of lines forming a “W” pattern. 14.The system defined in claim 11 in which said curable material depositionsystem dispenses droplets in a discrete pattern in a series ofindividual droplets.
 15. The system defined in claim 2 whichincorporates a photon-emitter component suitable as means forirradiating a surface selected from the group consisting of a UV lamp, alaser, a quartz heater and a radiative heater.
 16. The system defined inclaim 2 wherein thermal heating is accomplished through the mold. 17.The system defined in claim 2 wherein thermal heating is accomplishedthrough the substrate.
 18. The system defined in claim 2 whereinirradiation is accomplished through the mold.
 19. The system defined inclaim 2 wherein irradiation is accomplished through the substrate. 20.The system defined in claim 2 wherein orientation of said mold-substrateis automated and translation of the substrate and/or the mold isautomated.